The titer of synthetic fiber tows should be controlled as near as possible to the spinneret of the spinning frame, in order to detect, in good time, all the influences which arise from the spinning solution and from the conveyance thereof through the spinning pump. Hitherto attempts using conventional measuring methods have been unsuccessful, because the influences of heat, moisture and preparations on the tow have not permitted an accurate and drift-free measurement over a sufficiently-long period of time.
Above all, attempts using capacitive measuring methods have been made which, however, have not been successful. In particular, the nature of tows has hitherto interferred with optical measuring, for the most part, because of the band-shaped cross section thereof; the result of which is that the tows produce different measured values, depending on the orientation thereof in the light beam. If the influence on this form effect could not be entirely overcome, then it could indeed be reduced by applying specific measures. However, this was only possible while accepting a considerable expense in terms of apparatus. The stability of the prior optical measuring systems was also unsatisfactory over a long period of time.